Also known as validations and business logic. It's interesting that in web paradigm dynamic languages and low-level systems languages, defensive programming as

Also known as validations and business logic. It's interesting that in web paradigm dynamic languages and low-level systems languages, defensive programming assertions of invariants are widely dismissed. Validation and sanitizing of external input is often lacking and the source of many security issues. The problem domain is that most programming languages and application frameworks do a piss-poor job of separating and managing business logic around data storage and data mutation. MVC doesn't go nearly far enough. OTOH, there are fancy enterprisy business rule transaction systems that are divorced from most platforms. I think the key here is standardizing formal business rules in a portable "EBNF"/"markup" manner to be language and framework agnostic while not being laborious as COBOL-like Cucumber testing.